Note: Tanner '88 continues July 9, and is repeated July 23 & 30. The best way to find out how the political process works is to become a candidate; the next best way is to invent one. That's just what film director Robert Altman and "Doonesbury" cartoonist Garry Trudeau did for Tanner '88, the astonishing chronicle of Jack Quentin Tanner's presidential campaign. Wantonly mixing fact with fiction, the six-hour HBO series is a dizzy intrusion into the solemnity of the campaign process as it ran its course through the 1988 primaries. Altman's penchant for mercurial drama and Trudeau's acerbic wit combine in this always insightful, sometimes savage "mockudrama." Jack Tanner, played to the gleaming teeth by Michael Murphy, is an idealistic latecomer to the Democratic primary in New Hampshire. His team members, led by tough-as-nails T. J. Cavanaugh (Pamela Reed), bristle with high cynicism as they shape the all-important image of this presidential hopeful. Trudeau's back-room script fills us in on the manipulative mechanics of campaigning-the focus groups, photo ops, and info leaks. But the most uncanny spin in Tanner '88 is its giddy collision with the events of the actual primary. Tanner, whose campaign slogan is "For Real," continually bumps up against candidates as they stump the country. Cameos by Pat Robertson, Bob Dole, Gary Hart, meetings with Bruce Babbit, Kitty Dukakis and others add an eerie authenticity to our dark horse from Michigan. After several scandals, an attempted assassination, and an image makeover, Tanner and team head for Atlanta and the Democratic National Convention, where Tanner '88 mingles slyly with history. -Steve Seid